It's easy to understand for me, but I think the punctuation is incorrect, which could be confusing. Normally if you insert a clause using Dashes, the sentence fragment before the clause can be joined to the clause afterwards. However, in my opinion, the last dash should be a semi-colon. It is clear that 'evidence' is being presented as a word that defines what goes before it. The other part of it is 'hey Presto!' it is a phrase spoken by a magician right before he makes something appear. What he is making appear in this sentence is 'evidence'. Therefore, the evidence, is said to be a tricky or deceptive product of the activity that was described.

It's not a weird word arrangement, I'm afraid. This level of writing may be above your level of comprehension. I'm not sure how I can explain it to you, because "evidence, based on averaging results" is rather self explanatory in terms of structure. It may rather be that you're unfamiliar with this particular language that tends to be common in research: "averaging results" is the process of gathering a large sample set of data and finding an 'average' of those results, resulting in a higher likelihood of statistical accuracy. Thus, when it talks about "evidence, based on averaging results", it refers to the evidence collected, as evidence which is a product of those results which have been averaged..